Patent GB-1236061-A (GB)
Title: Methods of and apparatus for effecting bonds between workpieces
Inventor: CUSHMAN ROBERT HOLBROOK
IPC: H01L21/00
Filed: 1968-06-14
Abstract: 1,236,061. Welding by pressure; soldering. WESTERN ELECTRIC CO., Inc. 14 June, 1968 [15 June, 1967; 13 Nov., 1967], No. 28346/68. Heading B3R. In a method of bonding a plurality of electrical leads to respective conductive areas on a planar substrate utilizing a bonding tool having a planar bonding surface, either the bonding surface or the substrate is tilted during bonding so that a uniform pressure is applied simultaneously to the leads. In resistance welding, thermocompression welding, ultrasonic welding or soldering a semi-conductor device with beam leads to conductive areas on a substrate, either the workpiece support or the bonding tip are tiltable on a ball joint. Where the workpiece support is so mounted (Figs. 1-4, not shown) a resilient O-ring or a pad of neoprene rubber in the joint also permits a degree of lateral movement of the joint to obviate friction between the workpieces as they tilt while coming into contact, the beam leads of the semi-conductor device being mounted in the tip of the bonding tool and extending across the bonding surface and the conductive areas on the substrate being supported on the workpiece support. Apparatus for carrying out the method comprises a support 112 whereby the beam-leaded device 113 is correctly aligned with the bonding head 110. This alignment may be accomplished by means of an optical system. The bonding head 110 is then lowered by operation of a lever 174 until a tube 141 extending through the bonding tip contacts the device 113 which is then held against the end of tube 141 by a partial vacuum applied at the upper end of the tube. The pickup tube is then drawn upwards into the bonding tip by a compressed-air operated arrangement including a rocker arm 148 with a lobe 157 which bears on a clamp 144 for the tube 141. The clamp 144 is held in the raised position against the action of a spring 158 as long as compressed air is supplied to the cylinder 149. The tube 141 is held against rotation. The body portion 113<SP>1</SP> of the device 113 is drawn into an opening 162 in the bonding tip and the beam leads extend across the bonding surface 161. The bonding head 110 is raised to its initial position and the support 112 is pivoted out of the path of movement of the bonding head. A conveyer 111 is indexed to move a substrate S into the correct position beneath the bonding head and using the optical system, the conductive areas 117 on the substrate are correctly oriented relative to the beam leads 116 of the semi-conductor device. The bonding head is then lowered so that the beam leads 116 overlie respective conductive areas 117. When the device 113 engages the substrate, downward movement of the bonding tip 121 is terminated, since the tip is (as shown) of tapering longitudinal section and mounted in a correspondingly shaped bore in a support block 123, which continues its downward movement so that the bonding tip 121 is free to pivot about the ball 133 on which it is mounted. Relative vertical movement between the tip 121 and block 123 results in compression of a spring 137, which, acting on the tip 121 via the rod 132 and ball 133, results in the pressing of the beam leads 116 against the areas 117. Extra force is applied by means of the lever 174 and the tip 121 pivots so that the force applied to each beam lead is equal to that applied to the others. Heat is continuously supplied to the block 123 and hence the tip 121 by heating cartridges 124. Additional force may be exerted downwards on the device 113 by not retracting tube 141 but allowing it to be pushed upwards by force as the bonding head is lowered.